Want to add an external link to twenty ten navbar

Hi there

I’m trying to add an external link to the navbar of the twenty ten theme. I’ve looked around in header.php and added the link but it hasn’t worked properly as it has added a bullet point (which is hiding under ‘about me’) and changed the font.

https://psychicsuk.psychicreadingbyphone.co.uk/

Please could you let me know where I should be adding it.

Thanks so much for any help

Louisa